1. Field of the Invention
This invention relates to a sensor which detects mixing ratio of gasoline and alcohol employed to as a fuel of internal combustion engine for example.
2. Description of the Prior Art
Of these days, it is planned to extract liquid alcohol from plants. The alcohol thus extracted is mixed with gasoline to use as liquid fuel for internal combustion engine. When employed to an internal combustion engine for motor vehicle, it is necessary to precisely control the mixing ratio of the liquid fuel to obtain maximum output level and avoid adverse effect upon human health due to harmful exhaust gas. This precise control is naturally executed each time when the kind of the liquid fuel changes. When the mixing liquid of gasoline and alcohol is put into market, it is preferable that the mixing liquid is used together with the gasoline.
Therefore, it is an object of this invention to provide an improved sensor which is capable of continuously measuring a ratio of alcohol and gasoline with high precision in order to obtain most appropriate timing of ignition and injection when employed to an internal combustion engine.
According to the invention, a transparent column, both ends of which are supported by grips; the surface of said column is positioned in direct contact with a mixing liquid of gasoline and alcohol; a light emitting diode disposed so that light beams therefrom are incident on one end of said transparent column and the mixing liquid, said beams incident on said boundary at less than a critical angle being totally refracted, while said beams incident on said boundary at more than the critical angle being totally reflected to pass within said column so as to go out from the other end thereof, said critical angle depending upon a mixing degree of said liquid; a photo diode placed to receive the light beams reflected from said boundary so as to generate an output in accordance with the quantity of the light beams received; and said column being substantially determined its lengthwise and diametrical dimension such that the light beams incident upon said boundary at a critical angle, are allowed to totally reflect only once to enter said photo diode with the mixing ratio of alcohol and gasoline ranging from 100:0 to 0:100.